Off Axis Backscreen/Mirror Visual Display (OABD) systems are employed in simulator applications, e.g. simulators used for training pilots and other aircraft crew members. These systems typically have the drawback of a limited vertical field of view (FOV), usually about 40 degrees FOV. This limited FOV is often not enough to provide vision in areas necessary for multiple training tasks, such as the large downward FOV needed for landing training and large upward FOV needed for refueling training.
There is presently no known technique for obtaining a field of view larger than about 40 degrees in collimated visual displays such as the OABD system application. Although the use of a larger radius mirror might allow some increase in vertical FOV, mirror sizes much greater than those currently in use are just not practical due to several factors, including limitations in facility size, payload limitations (for systems on motion platforms), mirror manufacturing limitations, brightness impact, and cost.
Most OABD systems are also limited in resolution by both the projection device and the image generation system. Any increase in instantaneous vertical FOV negatively impacts the resolution of the system.
FIG. 1 shows one method used in the past few years whereby the entire display system is rotated about the observer eyepoint. This technique for increasing instantaneous vertical FOV is very complex because it requires moving structures, including mirrors, with a total system weight of almost 5,000 pounds in one application.
It would therefore be an advantage to provide an economical way to provide increased FOV for OABD systems.
A further advantage would be provided by an economical way to increase the total vertical FOV without impacting resolution.
Still another advantage would be provided by a system which increases the system resolution while maintaining the existing total FOV.